1. Field of the Invention
The present invention relates generally to analytical devices which are located on an optical disk, such as a compact disk (CD) or digital video disk (DVD). More particularly, the present invention relates to optical bio-discs including detection systems which form a part of such disk-based analytical devices.
2. Description of Related Art
Clinical chemistry involves the qualitative and quantitative analyses of body fluids, such as blood, urine and spinal fluid, as well as feces, calculi and other materials. Traditionally, clinical laboratories have been centrally located operations which utilized large and expensive automated equipment to run a multitude of different tests on large numbers of samples. A major problem with such centralized testing laboratories was and continues to be that the samples must be transported from doctors' offices and hospitals to the central laboratory. Transporting of biological samples is time consuming, costly and may result in the deterioration of the sample when it is not properly preserved.
The majority of automated analytical equipment which have been used in centrally located clinical laboratories require a relatively large amount of sample which is aspirated into the analyzer and split into a number of aliquots. Reagents required for each different assay are also aspirated into the analyzer. The various aliquots of sample and reagents are pumped via a peristaltic pump through complex arrangements of tubes and reaction chambers to achieve the desired chemical reactions. One or more skilled technicians are required to run the analyzer and constantly monitor the pumping system to insure that samples and reagents are flowing properly through the system. Constant maintenance of these large and complex analyzers is essential to insure that none of the multitude of tubes and passageways become blocked.
More recently, there has been a trend towards decentralization where the majority of routine clinical chemistry testing is done on smaller instruments which are located in the doctors office or hospital. A host of small analyzers have been developed which rely on centrifugal force to move samples and reagents through the analytical system. These units are well-suited for use in hospital laboratories and doctors offices because they eliminate the complexities associated with the larger pump driven autoanalyzers. These rotor or centrifuge based systems are stand alone units which tend to be expensive and require at least some training to operate. Accordingly, they have been limited to use in hospitals and doctors offices.
An even more recent development has been the discovery that optical disks, such as CD's and DVD's can be utilized as platforms for performing centrifuge-based analytical chemistry. In addition to functioning as a centrifuge, the optical disk can store information which can be used to control the analytical procedure. Further, the laser used in all CD and DVD players provides an especially useful built-in optical detector system. These laboratories on a disk are described in International Publication Number: W098/38510. The optical disk based analytical devices are extremely versatile and can be used by anyone who has access to a personal computer which includes a CD or DVD unit.
A feature of optical disk-based analytical devices is that they require relatively small amounts of blood or other sample fluid. This is desirable since there has been a continuing push in clinical chemistry to develop analytical devices which use smaller and smaller amounts of sample material. Sample size becomes especially critical in newborn babies and the elderly. However, as sample size decreases, the number of analyte molecules present in the sample also decreases. For extremely small samples, the number of analyte molecules which may be present can be on the order of a few hundred. In addition, there are situations where it is desirable to detect extremely low concentrations of analyte in a sample. As a result, there is a need to provide detection systems for optical disk-based analytical devices which are capable of detecting extremely small amounts of analyte in an accurate and reproducible manner.